The Use of Hyperspectral Imaging for Remote Sensing, and the Development of a Novel Hyperspectral Imager

This thesis determines the potential uses of a novel technology in hyperspectral remote sensing, by testing the capabilities of a prototype imaging spectrometer that was built using microslice technology. These capabilities are compared to those of current hyperspectral remote sensing instruments in the context of the requirements for various remote sensing applications. Due to the wide variety of potential applications for hyperspectral imaging, any unique capability of a new instrument is likely to improve a current application, or even develop a new one. The use of microslice technology allows a 2-dimensional eld of view (FoV) to be imaged simultane ously with a wide spectral range. Modelling of the remote sensing performance of the spectrometer shows that this enables it to achieve a signal to noise ratio (SNR) an order of magnitude higher than conventional hyperspectral instruments. The prototype microslice spectrometer images in the 475-650 nm wavelength range at 7 nm spectral resolution. It also images an instantaneous eld of view (IFoV) of 260 x 52 mrad, at a spatial resolution of 2.6 mrad. Classication techniques are used on ground based laboratory and eld test data from the instrument to demonstrate that it can accurately identify some mineral, vegetation, and water pollutant samples. Various trade-os can theoretically be performed on the prototype specications to develop an instru ment with particular capabilities for a specic application. This novel design means that a greater detector area is required than for conventional designs; but the 2-dimentsional FoV gives greater trade-o exibility, in particular allowing the SNR to enter into the trade-o equation. This unique capability was found to lend itself to two applications in particular: detecting water pollutants in rivers, and detecting hydrocarbons contamination of ecosystems

Innovative technologies for terrestrial remote sensing

[In lieu of abstract, extract from first page] Characterizing and monitoring terrestrial, or land, surface features, such as forests, deserts, and cities, are fundamental and continuing goals of Earth Observation (EO). EO imagery and related technologies are essential for increasing our scientific understanding of environmental processes, such as carbon capture and albedo change, and to manage and safeguard environmental resources, such as tropical forests, particularly over large areas or the entire globe. This measurement or observation of some property of the land surface is central to a wide range of scientific investigations and industrial operations, involving individuals and organizations from many different backgrounds and disciplines. However, the process of observing the land provides a unifying theme for these investigations, and in practice there is much consistency in the instruments used for observation and the techniques used to map and model the environmental phenomena of interest. There is therefore great potential benefit in exchanging technological knowledge and experience among the many and diverse members of the terrestrial EO community

New opportunities of freeform gratings using diamond machining

With the recent development of new ultra fine aluminium alloys and progress in the field of directly machined freeform surfaces, diamond machined freeform gratings could play an important part in future spectrographs or integral field units, particularly at SWIR and LWIR wavelengths where the improved thermal performance of metal optics at cryogenic temperatures is well established. Freeform diamond machined gratings can offer a cost-effective, compact, and flexible alternative to gratings fabricated by other methods such as ion beam etching or complement these technologies. In this paper, both the advantages and limitations of 5 axis diamond machined freeform gratings are presented and potential applications are discussed

Photonic Spectroscopy in Astronomy

This thesis investigates photonic spectroscopy and its use in astronomy. In chapter two the theory associated with both astronomical spectroscopy and photonic spectroscopy is shown. The convergence of the two in the field of astrophotonics is discussed along with existing work in the field. In chapter three models of the Integrated Photonic Spectrograph are created and compared like-for-like with existing instruments. The results suggest that the Integrated Photonic Spectrograph will be similar to existing instruments in terms of size and will require more detector pixels for a full instrument. In chapter four the modelling is extended, examining the areas where pho- tonic spectroscopy could show advatanges over conventional instrumentation. This is done by varying spectral resolution, telescope diameter, seeing and num- ber of objects sampled. The results show that the Integrated Photonic Spec- trograph will perform best when the telescope is close to the diffraction-limit, both in terms of size and number of detector pixels required. Science cases are presented for these areas. In chapter five different concepts for a redesigned Integrated Photonic Spec- trograph are presented and the advantages and disadvatanges of the variations are commented upon. The two that are chosen for development require the telescope Point Spread Function to be reformatted to a long slit. This device, which we have named the photonic-dicer is presented in chapter six. Its design, manufacture and testing is discussed both in the laboratory and on sky in conjunction with the CANARY adaptive optics system. Finally chapter seven presents our concluding remarks and discussions for future work

New Microslice Technology for Hyperspectral Imaging

We present the results of a project to develop a proof of concept for a novel hyperspectral imager based on the use of advanced micro-optics technology. The technology gives considerably more spatial elements than a classic pushbroom which translates into far more light being integrated per unit of time. This permits us to observe at higher spatial and/or spectral resolution, darker targets and under lower illumination, as in the early morning. Observations of faint glow at night should also be possible but need further studies. A full instrument for laboratory demonstration and field tests has now been built and tested. It has about 10,000 spatial elements and spectra 150 pixel long. It is made of a set of cylindrical fore-optics followed by a new innovative optical system called a microslice Integral Field Unit (IFU) which is itself followed by a standard spectrograph. The fore-optics plus microslice IFU split the field into a large number of small slit-like images that are dispersed in the spectrograph. Our goal is to build instruments with at least hundreds of thousands of spatial elements

New Microslice Technology for Hyperspectral Imaging

We present the results of a project to develop a proof of concept for a novel hyperspectral imager based on the use of advanced micro-optics technology. The technology gives considerably more spatial elements than a classic pushbroom which translates into far more light being integrated per unit of time. This permits us to observe at higher spatial and/or spectral resolution, darker targets and under lower illumination, as in the early morning. Observations of faint glow at night should also be possible but need further studies. A full instrument for laboratory demonstration and field tests has now been built and tested. It has about 10,000 spatial elements and spectra 150 pixel long. It is made of a set of cylindrical fore-optics followed by a new innovative optical system called a microslice Integral Field Unit (IFU) which is itself followed by a standard spectrograph. The fore-optics plus microslice IFU split the field into a large number of small slit-like images that are dispersed in the spectrograph. Our goal is to build instruments with at least hundreds of thousands of spatial elements